High frequency tuning system



Oct. 4, .1932. H. F. ELLIOTT HIGH FREQUENCY TUNING SYSTEM Filed June 28.1926 4 Sheets-Sheet 1 W Aiioz'rzey Oct. 4, 1932. H. F. ELLIOTT 1,880,933

HIGH FREQUENCY TUNING SYSTEM Filed June 28, 1926 4 Sheets-Sheet 2 luau75 .Zizvazziar hi a/d E 5/0/74 y m/ AZZoIiZtj/ Oct. 4, 1932. H. ELLIOTT1,880,933

HIGH FREQUENCY TUNING SYSTEM Filed June 28, 1926 4 Sheets-Sheet 4 S w Wn N3 Mfl Sx f E Q n F QM? w A g $3 QQ M 1R.\\ @Q MD J WW 1 \Q 40. v\ y sQ g NQ Nw\\ Patented Oct. 4, 1932 UNITED STATES PATEN OFFICE HAROLD F.ELLIOTT, OF PALO ALTO, CALIFORNIA, ASSSIGNOR, MESNE ASSIGNMENTS,

TO RADIO CORPORATION OF AMERIGA, DELAWARE OF NEW YORK, N. K, ACORPORATION OF HIGH FREQUENCY TUNING.- SYSTEM Application filed Jane 28,

This invention relates to the tuning of electrical circuits arranged tocarry high frequency currents, such for example, as is en countered inradio apparatus, either for transmitting or for receiving.

It is now well-known that when dealing with high frequency electricalenergy, the degree of response to such energy by a circuit can be verymaterially enhanced by tun ing the circuit so that it will be resonantto the frequency at which the energy is transmitted. In this way, it isnot only possible to increase the response, but also to render thesystem selective as regards frequency. All this is well understood, andis utilized most often in connection with radio receivers, so that thesignals from a plurality of stations can be segregated by this tuningprocess.

In many instances, the mere provislon of one or two tuned circuits isinsufficient to provide the desired degree of selectivity, and toovercome this effect, the advent of several stages of radio frequencyamplifiers in cascade has taken place in the past few years. Eachamplifier stage, besides increasingthe amplitudes of the e. m. f.sreceived, provides in addition, a tunable circuit; and all or" the tunedcircuits contribute to render the receiver a great deal more selectivethan when only a few tunable circuitsare used.

The tuning of the circuits can be accomplished'in any one of severalways. For example, a variable condenser or a variable inductance can beincorporated in each of the circuits, and one or both of such elementscan be operated until the desired resonance 1s obtained. It has alsobeen common to attempt simultaneous tuning of all out the associatedtunable circuits, by providing a unit control for all of the tuningelements. For instance, the rotors of all of the variable elementshavebeen mounted on a common shaft, or else arranged to be moved in unisonby a common motion transmitting device.

At first blush, it appears entirely feasible to secure simultaneous andaccurate tuning of all of the circuits in this manner. When it isconsidered however, that very high frequencies are dealt with, itbecomes evident 1926. Serial No. 119,114.

that apparently minute efi'ects, incapable of being compensated in thismanner, can have serious deleterious results upon the selectivity of thesystem. For example, slight variations from absolute uniformity of theparts making up the tuning element cause sufficient variations indistributed capacity or stray inductance to cause a large variation inthe resonance settings.

Another disturbing feature is that the stray electrostatic andelectromagnetic fields have necessarily no uniform variation for all ofthe tuning elements, as they are simultaneously moved. Thus it happensthat even if enact resonance be secured simultaneously for one setting,there is no assurance that such exactitude persists for any othersetting.

Some systems in the past have attempted to overcome these disadvantagesof single unit control by providing supplementary con trols for all butone of the units; but it is evident that in many respects thisarrangement would be as bad as a series of independently controlledtuning devices. Another proposal was to design the tunable circuits sothat their resonance curves are broad. This is highly objectionable, forit largely nullifies the selectivity which it is aimed to secure by asuccession of tuned circuits; and besides, the eiiiciency of the set isvery ma terially reduced.

lit is one of the objectsof my invention to make it possible to obviateall these disadvantages of a unit control system.

It is still another object of my invention to provide a unit controlsystem that can be accurately and permanently adjusted over the entirerange of operation of the system so that all of the circuits remainaccurately in step for that range.

It is another object of my invention to compensate for the inherentinaccuracies in the parts making up the tuning elements, whereby lesscare need be exercised to build and assemble such parts. I

My invention can be applied readily to all forms of variable tuningdevices. For example, in connection with measurement of wave lengths orfrequencies, it is necessary to calibrate the wave meter readingscareful- 1y for each instrument, due to the unavoidable small variationsin the parts making up the wave meter. With the aid of my invention, thedial or other form of scale can be printed in large quantities, and thevariable tuning element can be readily adjusted so as to make theresonance conditions coincide with the scale readings. Therefore it isanother object of my invention to make it possible to provide controlapparatus for receivers, wave meters, or the like, which ma be adjustedto correspond with the indications of the scales upon which thefrequencies are permanetly marked in advance of the assembly of theparts; thus these scales can be produced in quantities, in well-knownways without the necessity of hand calibration for each individual dialor scale.

It is still another object of my invention to make it possible to fixthe characteristic tuning curve of the tuning device so. as to give anydesired form of curve; thus it may be desirable to have the frequency ofresonance, or the wave length of resonance, vary as a straight line whenplotted against the amount of movement of the controlling member; andwith my device, such characteristic curves or curves of other formsalso, can be produced in a simple and inexpensive manner.

It is still another object of my invention to make it possible to alterexisting receiving sets so that they may have the advantageshereinbefore discussed, yet with little ex ense.

y invention possesses manv other advantages, and has other objects whichmay be made more easily apparent from a consideration of severalembodiments of my inven tion. For this purpose I have shown a few formsin the drawings accompanying and forming part of the presentspecification. I shall now proceed to describe these forms in detail,which illustrate the general principles of my invention; but it is to beunderstood that this detailed description is not to be taken in alimiting sense, since the scope of my invention is best defined by theappended claims.

Referring to the drawings Fig. 1 is a back view of an adjustable tuningdevice mounted on a receiver panel and embodying my invention;

Fig. 2 is an end view of the panel and device of Fig. 1, as seen fromplane 55 of Fig. 1;

Fig. 3 is a back view of one of the tuning elements, with a few of theassociated parts, taken along plane 66 of Fig. 2, and having a few partsbroken away;

Fig. 4 is a view of the panel shown in Fig. 1, from plane 77, some ofthe parts being broken away;

Fig. 5 is an enlarged sectional view of one of the operating devices fora tuning element, taken along plane 88 of Fig. 3;

Fig. 6 is a sectional view taken along plane 9-9 of Fig. 5;

Fig. 7 is a view taken from plane 10-10 of Fig. 5;

Fig. 8 is a front elevation, partly diagrammatic, and partly in section,of a modified form of my invention;

Fig. 9 is a top plan view of the form shown in Fig. 8;

Fig. 10 is a sectional view, taken along plane 1313 of Fig. 8;

Fig. 11 is a view, partly in section, of still another form of myinvention;

Fig. 12 is a sectional view, taken along plane 1515 of Fig. 11;

Fig. 13 is a detail sectional view taken along plane 1616 of Fig. 11;

Fig. 14 is an enlarged detail of a portion of the apparatus, indicatedby arrow 14 on Fig. 11; and

,Fig. 15 is a sectional detail taken along plane 18-18 of Fig. 14.

One form of my invention is illustrated in Figs. 1 to 7, and will now bedescribed.

In the present instance, all of the parts are shown as mounted on theback of a panel 77. A metallic sub-base 78 is used to conceal the wiringon the rear surface of the panel. 0n the sub-base can be mounted theradio frequency elements, such as tubes 42, as well as the radiofrequency transformers, such as 79, and variable condensers, such as 40.In order to ensure against variations in stray capacity, such as due tobody ca acity or the like, and also to serve as shields or the radiofrequency parts, metal screens 80 are provided. Each of these screens isassociated with one radio frequency unit, including the tube, the radiofrequency transformer, and the variable condenser associated with thetransformer. These screens form, with subbase 78, completely enclosedspaces for these elements. Five such screens are indicated in Fig. 4,but of course the number can be varied, and depends upon the number ofradio frequency circuits utilized.

Each of the variable condensers, such as 40, is provided with anoperating member, such as shaft 81 which in this instance extendsslightly out of the side of its screen 80, and has an axis parallel withthe horizontal edge of panel 77. Although any particular kind of tuningelement is not essential to the invention, nevertheless I shall nowbriefly describe the form which is indicated in the drawings.

In the present instance, the condenser 40 includes a pair of parallelshafts, one of which is 81, and the other 82. These are supported oninsulation standards 83, supported on the top of the correspondingscreen 80. They are geared together to rotate in unison, by gears 84 and85. Each shaft carries a set of metallic plates 86 and 87. All of theplates on each shaft are electrically connected, but

esaeea are insulated from their shafts. As shaft 81 rotates, the plates86 and 87 interleave, and the extent of the interleaving determines theefleetive capacit between the sets. The overlapping of t e plates beginsat the corners, as indicated in Fig. 5, whereby a straight line wavelength characteristic is obtained.

Each of the projecting shafts 81 carries an operating arm 88, the freeend of which has a'cam roller 89. These arms are arranged to be moved bythe aid of a common motion transmitting mechanism, but not necessarilyin unison. To secure this effect, a shaft 90 is provided, in thisinstance parallel to shafts 81, and journaled in bearings 92 on base 78. The shaft carries a series of cams 93 arranged to rock the arms 88 byacting on roller 89. Each cam is adjustable so that the correspondingcondenser movement can be compensated to give accurate adjustments forall positions of shaft 90.

The cam structure is disclosed most clearly in Figs. 8, 9 and 10, and ismerely representative of the class of adjustable cams. It includes abody portion 9a (in the present instance in the form of ahalf-heart),fastened as by screws 95 to shaft 90, said screws passing through a hub96 on body 94. The body has flanges 97, which extend completely aroundthe cam 93, although the body portion 94 terminates at the tip of theheart.

The roller 89 is guided between these flanges, and rests on the camsurface proper, formed by one or more flexible non-rigid strips 98extending around the heart shaped body 94, and anchored as by screws 99to hub 96. In the present instance, two strips are shown, of flexiblemetal such as phosphor bronze, the outer one projecting beyond the innerone and looped over the end of a spring wire 100. This spring serves totension the outer cam strip 98; it is of U shape, the ends of the legsbeing anchored at hub 96, and the connecting portion being looped asclearly indicated, by the outer strip 98.

It is evident that as thus far described, the strips 98 are confinedover body 9 1 and held in place by spring tension. The shape of the camsurface can be varied at will however, by a series of set screws 101that project through body 94 and engage the inner strip 98. Byindividual adjustment of these screws, the non rigid cam face can bemade to compensate for irregularities in the tuning characteristics.These screws can readily be reached by a screw driver extending betweenthe legs of the spring 100.

By properly fashioning body 94, it is evident that subsequent tineadjustment of screws 101 can be readily made to give any desiredcharacteristic to each of the condensers, such as straight line wavelength, or straight line frequency. Adjustment of screws 101 can beresorted to for making scale readings accurate, even when such scalesare produced cheaply in quantity. It is also evident that due to thenon-rigid character of the active cam surface, it is possibleindependently to adjust relatively small increments of that surface, andwithout disturbing its continuous character.

In connection with radio receiving sets, the adjustment of thecondensers during the process of assembly, is a simple matter. The shaft90 is set in succession, at several distinct points, and for eachsetting, the cam screw 101 nearest the rollers 89 for that sett'ng areadjusted to bring all of the condensers into proper position forresonance condition of their associated circuits. Preferably thesettings are such that the rollers 89 come directly over one of thescrews 101 for each setting. Then shaft 90 is set to a new setting, andthe process repeated. After adjustment of all of the screws 101, thenonrigid cam surface is of the proper shape to ensure uniform variationof the associated circuits.

In order to keep roller 89 on the cam track, a resilient force is used,as for instance that exerted by a helical spring 102 (Fig. 3) acting onshaft 82 to urge gears 84 and 85 in a direction to decrease thecapacity; this resilient force being overcome by the action of cam 93,urging roller 89 in a position to rotate wheels 84 and 85 to increasethe capacity.

The shaft 90 can be rotated in any convenient manner. For example, itmay carry a worm wheel 103 at one end, engaged by a worm 10 1. The wormis fastened to a transverse shaft 105 suitably journaled in a stationaryguide 106 (Fig. 1), and carrying a worm or spiral gear 107 at its otherend. This in turn can be rotated by the aid of a gear 108 fastened onshaft 109 on which handle 91 is fixed for manual operation.

It is not essential to utilize any particular kind of tuning element.and 10, a pair of a modified form of tuning device is shown, operated bya common shaft 110. This'shaft cariresthe usual form of rotary plates111 of a variable condenser.

The cooperating plates 112 are in this instance rectangular, and aremounted in spaced relation in a pair of insulation blocks 113 and 114.These plates, instead of being stationary, are movable about the pivot115 passing through the support 11 1 and supported in clip 116. Thearrangement is such that as shaft 110 rotates, adjusting the position ofplates 111, plates 112 may also be mounted as by the aid of hub 119, onshaft 110. Flanges are provided for forming a groove for the followerroller 121, which is mechanically connected to the plates 112, asthrough the arm 122 and link 123. Arm 122 is pivoted on stationary pivot124, and is urged to cause roller 121 to engage cam 117, by the spring125.

The flexible strips 117 forming the adj ustable cam surface are anchoredas at 126 to one end of body 118. The free end of the outer strip isheld to the end of how spring 127 by loop 128, this spring pulling thestrips against the adjustable set screws 129. The legs of spring 127 aredriven into hub 119 and are thus held in lace.

The manner of adjusting the condensers is substantially the same as thatdescribed in connection with the first form. The main difference in themode of operation-is that the compensation is secured by small angularvariations of the plates 112 about pivot 115.

A still further modification of the compensating arrangement isillustrated in Figs. 11 to 15 inclusive. In this form, condensers suchas illustrated in Figs. 2 and 3 are again used, each having two sets ofmovable plates 130, and 131, with intermeshing gear segments 132 and133. As before, a helical spring 134 (Fig. 12) tends to separate theplates, the separation being limited by the cam arrangement to be nowdescribed.

A supporting panel 135 has fastened thereon bearings 136 for the shafts137 and 138 of the condensers, which may be held in proper position byany appropriate means. Each shaft 137 carries a forked arm 139 formoving th shaft. Movement is imparted to the arm by a series of links140 and 141, from an actuator arm 142; all of the actuator arms aremoved in unison by a rod 143, moved in turn manually by a lever 144having a hand knob 145. Rod 143 passes through the fork of arm 139. Thelinks 140 and 141 determine the extent of movement of arm 139, and thusthe extent of the corresponding condenser, by the aid of an adjustablecam strip 146. This strip coacts with roller 147 carried by pivot 148joining the links 140 and 141. It is evident that due to th resilientforce exerted by spring 134 on shaft 138, the roller 147 will beresiliently urged against this cam face, the face serving to limit therelative movement of links 140 and 141. The cam strip 146 is supportedat its left hand end on top of block 149, which is fastened to a cambody 150.

Another block 151 below block 149 serves with that block to confineanother strip 154. Between the strips 149 and 151- there is a flexibleresilient element such as a coiled spring 152. Set screws 153 in body150 operate on strip 154 to vary its configuration, and through thespring 152, that of cam strip 146. The spring 152 serves efiiciently toeliminate unevenness in the cam surface, as is apparent.

The free ends of strips 146 and 154 are slidable on short strips .155and 156 held in proper spaced relation by the aid of blocks 157 and 158fastened to body 150 by screw 159. The ends of strips 146 and 154 areslotted, as indicated at 160, Fig. 18, to encompass this screw andfurther to guide the movement of this free end during the process ofadjustment of cam screws 153. Flanges 161 are located on each side ofbody 150, and these flanges as well as the body are supported on block162, Fig. 12, fastened to panel 135.

- The mode of operation of this embodiment is probably entirely clearfrom what has been said with regard to the other forms. The maindifference resides in the fact that the condensers are mounted side byside instead of in tandem arrangement; and that a concave cam isused'instead of a convex one. It is evident that since spring 134 tendsto rotate gear segment 132 in clock-wise direc tion, and that since theposition of arm 142 is fixed by bar 143, arm 139 can move in a counterclockwise position only far enough to cause engagement of roller 147with the cam surface. By adjusting the cam surface, the relativemovement of arm 139 and that of arm 142 is accurately controlled,thereby providing an accurate and simple compensation for all positionsof the bar 143.

Although several modifications of the invention have been outlined, yetthey all rest upon the common conception that the law of variation of aseries of tuning elements can be independently adjusted, even when acommon actuating means is provided for all of them. It is this featurethat makes the invention so well adapted to maintain a series ofcircuits in exact resonance for all positions of adjustment, and therebyto maintain a high degree of selectivity without the inherentdisadvantages common in other forms of tuning devices.

I claim:

1. In a tuning device having a plurality of separate variable tuners anda common means for directly actuating the movable elements of saidtuners, the improvement which comprises an additional adjustableoperating means, for precise adjustment, operated by said common means,said additional means including a cam comprising a body having an archedsurface, adjusting screws projecting through said surface and a flexiblestrip resiliently held against the projecting ends of said screws andforming an adjustable cam surface.

2. In combination, a plurality of separate variable tuners for highfrequency circuits, a common means for actuating said tuners, and inaddition, adjustable cams for precise adjustment of said tuners,actuated by said common actuating means, said cams each comprising abody, and a separate strip forming an adjustable cam surface,resiliently held toward said body, and adjusting screws for determiningthe configuration of said cam surface whereby the movable elements ofsaid tuners may be brought into precise adjustment throughout theiroperating range.

3. In combination, a plurality of separate variable tuners, havingrelatively movable elements, an actuator for each tuner positivelyconnected thereto, a common operating means for said actuators, andadjustable cam means actuated by said common means for effectingrelative movement of said elements independently of that caused by saidactuators, said cam means comprising a body having convex surface, aseries of adjusting screws projecting through said surface and a stripforming an adjustable cam surface resiliently held in contact with theprojecting ends of said screws.

4. In combination, a plurality of separate variable tuners for highfrequency circuits, each tuner comprising elements relatively movable,actuating means for each tuner positively connected thereto, a commonrotary operating means for said actuating means, one element of eachsaid tuner being mounted for movement independent of that due to itssaid actuating means, a separate actuator for each said one element,adjustable cam means connected to said common operating means foroperating said separate actuators, said cam means comprising a bodycarrying a flexible strip formin an adjustable convex cam surface, theconfiguration of said surface being determined by screws projectingthrough said body and against said stri 5. In combination, a pluralityof variable tuners for high frequency circuits, each tuner comprisingelements movable with respect to each other, actuating means for eachtuner to cause relative movement between the respective elementsthereof, a common operator to operate said actuating means in unison,one element of each tuner being mounted for movement independent of thatcaused by the said actuating means, a separate actuator for each of saidone elements, cam means actuated by said common operator for actuatingsaid separate actuators, said cam means comprising a rigid cam bodyhaving an arched surface, a series of set screws projecting through saidsurface, and a flexible laminated strip resiliently stretched over theprojecting ends of said set screws to form a continuous adjustable camsurface.

6. In combination a plurality of separate variable tuners for highfrequency circuits, each tuner comprising a stator and a rotor,actuating means for each tuner to cause relative movement between thestator and rotor thereof, a common operator for operating said actuatinmeans in unison, the stator of each tuner being mounted for relativemovement independent of that caused in the rotor by its said actuatingmeans, a separate actuator for each of said stators, adjustable camsactuated by said common operator for operating said separate actuators,each of said cams comprising a rigid grooved cam body, a flexible striplying in said groove forming an adjustable cam surface, meansresiliently urging said strip toward the bottom of said groove, and aseries of set screws projecting through the bottom of said groove, andadjustable in said body for varying the contour of said adjustable camsurface.

7. In combination a plurality of separate variable radio frequencytuners, each having a rotor and a stator, actuating means positivelyconnected to each rotor, common operating means for said actuatingmeans, said stators mounted for movement with respect to said rotorsindependent of that due to said actuating means, separate actuators forsaid stators, separate adjustable cams moved by said common means toeffect movement of said actuators, said cams each comprising a rigidbody having an arched surface, and a flexible strip forming a camsurface, the configuration of said surface being determined by a seriesof set screws pro ecting from within said body into contact with saidstrip and resilient means holding said strip in contact with theprojecting ends of said set screws.

8. In an electrical system having a plurality of continuously variablereactors for regulating the reactance characteristics of the system overa range of frequencies, a primary control actuating the reactors inunison and adjusting each to approximately the required reactance foreach setting of said primary control, and a secondary control for eachreactor connected to operate ,in unison with the primary control, saidsecondary controls providing adjustable means for slightly increasing ordecreasing the reactance of each reactor independently of the others andindependently of the adjustment imparted to it by the primary control,said secondary controls each comprising a cam body having a convexsurface, a series of adjusting screws projecting through said surfaceand a flexible strip, forming an adjustable cam surface, resilientlyheld in contact with the projecting ends of said screws.

9. A tuner, an actuator therefor, and means for precisely controllingthe motion of the tuner relative to the actuator including an adjustablecam, said cam characterized by the following constructional features, arigid body, a flexible strip overlying said body and forming anadjustable cam surface, adjusting means, over which the strip may slidefreely longitudinally, for adjusting the contour of said strip relativeto said body, and means longitudinally stressing said strip whereby thestrip is resiliently held against the said adjusting means.

10. In combination, a plurality of separate variable tuners and meansfor precisely adjusting each tuner including an adjustable cam havingthe following elements in combination, a rigid body having asubstantially circular portion, a series of set screws radial- 1yarranged in and projecting through said portion, said screws beingaccessible from the concave side of said portion for adjustment in saidbody, a flexible strip overlying the projecting outer ends of saidscrews and means stressing said strip longitudinally and resilientlyholding the strip against the pro jecting ends of said screws therebyforming an adjustable cam surface.

11. In a receiving system having continuously variable tuners and acontrol for actuating said tuners in unison, the improvement whichincludes an adjustable cam and follower means actuated by said controlfor precise adjustmentof each of said tuners'independently, each camcomprising a rigid body and screws projecting through said bod andadjustable therein, a fiexi le strip reely overlying the projecting endsof said screws and forming a cam surface, the contour of the cam surfacebeing determined by said screws and limited to curvature in onedirection but not limited as to radius of curvature, and spring meansresiliently urging said strip into contact with the projecting ends ofsaid screws.

12. In combination, a plurality of variable tuners for high frequencycircuits, an actuator for each tuner, a cam for each actuator fordetermining its law of motion, said cam having a cam body, as well as aflexible strip forming a cam surface, said cam also having means forresiliently stretching said strip over the body, as well as means foradjusting the configuration of said strip and adjustable in said body,and a common means for causing relative motion between each cam and itsactuator.

13. In combination, a shaft, a series of cams on said shaft, and avariable tuner for high frequency circuits controlled by each relativeto the fixed point and the adjusting means durin the process ofadjustment.

- 15. In com ination, a plurality of variable tuners, and a common meansfor adjusting the tuners, comprising means forming a continuous camsurface, fixed at one point for operating each tuner, and means foradjusting said surface at a plurality of points other than said fixedpoint, said adjusting means and the cam surface being arranged to permitfree longitudinal movement of the cam surface relative to the fixedpoint and'the adjusting means during the process of adjustment.

16. In combination, a variable tuner having relatively movable members,means forming a conformable cam surface for causin re ative movementbetween the members, said surface bein movable longitudinally withrespect to a xed point at which it is secured and a plurality of meansforming adjustable points over which the cam surface conforms,

said means being closely spaced and permitting the cam forming means tomove thereover with respect to the fixed point, whereby said conformablesurface is caused to present a continuous smooth curve throughout itsactive length.

17. In a radio apparatus, the combination of a variable tuner, a camhaving an adjustable surface for controlling said tuner, and means foradjusting the surface of said cam at a plurality of points, said camsurface bem fixed at one point against movement and ing free to movelongitudinally there from to assume a substantlally smooth andcontinuous curvature through and between the adjusting points.

In testimony whereof I have hereunto set my hand.

HAROLD F. ELLIOTT.

cam and arranged to be varied thereby, each of said cams comprising acam body, a flexible strip forming a cam surface, set screws in saidbody for adjusting the configuration of the strip, and meanslongitudinally stressing said strip whereby the strip is resilientlyheld against said set screws. 14. In combination, a variable tunerhaving relatively movable members, means form in a continuous camsurface fixed at one point for causing relative movement between themembers, and means for adjusting said surface at a plurality of pointsother than said fixed point, said adjusting means and the cam surfacebeing arranged to permit free longitudinal movement of the cam surface

